The present invention relates to a system for detecting the neutral state of a transmission for an engine for vehicles.
Heretofore, an engine speed control system has been provided for controlling the engine speed. The system is, for example, adapted to control idling speed to a desired idling speed by adjusting the amount of air or the amount of the air-fuel mixture to be induced in the engine in dependency on an error signal which is the difference between a desired reference idling speed and the detected idling speed. In such an automatic, engine speed control system, the detecting of the neutral state of a transmission is necessary.
A conventional neutral state detecting system comprises a clutch switch provided adjacent to a clutch pedal of the vehicle and a neutral switch provided in the transmission. The neutral state detecting system operates to judge the neutral state of the transmission from two signals obtained by the above described switches for producing a neutral signal.
However, since the neutral switch is provided in the transmission, the switch is complicated in construction and expensive.
The object of the present invention is to provide a neutral state detecting system which reliably detects the neutral state and which has a simplified construction.
According to the present invention, there is provided a system for detecting the neutral state of a transmission for an engine mounted on a vehicle comprising an engine speed detecting means for producing an engine speed output signal proportion to the engine speed; a vehicle speed detecting means for producing a vehicle speed output signal in proportion to the vehicle speed; an operation circuit for judging whether the ratio of the engine speed output to the vehicle speed output is in a transmission ratio range dependent on the transmission; the operation circuit being so arranged as to produce at least one neutral state output when the ratio is not in the transmission ratio range.
Other objects and features of the present invention will be fully described with reference to the accompanying drawings.